http://dvice.com/archives/2008/08/styrofoam_dome.php
Check out the pictures, they actually look decent on the inside. If you got four of them connected, you could live in a pretty good sized dome home. I wonder if you could flip one of the domes upside down, bury it to ground level and connect the top dome to it... Then you could live in a duplex sphere.
I'd get one and layer dirt up the sides and on top, grow grass all over it and live like a hobbit.